CN101080578A - End profiled construction for surface pressure reduction on complementary plain bearing elements - Google Patents

Abstract

The invention relates to an end-forming contour on a complementary element of a plain bearing, comprising a pin (22) and at least one bearing bush (24, 24 ') which accommodates the pin (22), wherein the pin is subjected to an eccentric force (F) acting perpendicular to the pin-bearing bush unit (20), and the at least one bearing bush (24, 24') is of cylindrical design, and the pin (22) is of tapered design, starting from a predetermined position, in each case in the axial end direction. The invention also relates to the geometrically opposite geometry of the pin and the bearing bush.

Description

End profiled construction for surface pressure reduction on complementary plain bearing elements

technical field

The invention relates to an end profile structure (Endprofilierung) for reducing surface pressure on a sliding bearing complementary element (Gleitlagergegenlaufpartnern), comprising a pin and at least one bearing bush receiving the pin, wherein the pin bears a vertical direction Eccentric force acting on the pin-bearing-bush unit.

Background technique

Axial units are known which consist of a pin and at least one bearing bush which receives the pin radially, wherein the pin and the bearing bush form complementary plain bearing elements which are assigned to each other. In this case, the pin can absorb a force acting perpendicular to the pin-bearing bush unit (sliding bearing), which acts on the pin centrally or eccentrically.

In particular in commercially available belt tensioning systems, a fastening arrangement consisting of a pin-bearing bush unit of this type is common. Used in belt tensioning systems such as control engines or equipment engines of vehicles with internal combustion engines.

Belt tensioning systems are known from the prior art which have a tensioning pulley arranged eccentrically with respect to the pin-bearing bush unit, which is rotatably mounted via an eccentrically arranged roller bearing. It has been shown in the past that in the case of pin-bearing bushing units with tensioning system with eccentrically arranged tensioning pulleys, marginal loads occur between the pin and the bearing bushing. This results in a higher pressure per unit area on the pin and bearing bush, so that the service life of the slide bearing may be reduced. Especially in the case of high eccentrically acting forces and long-term operation, this can lead to an inclination, so that overall the guide with tensioning system is not sufficient for trouble-free operation.

Prior to this background, DE 195 33 457 A1 disclosed a tensioning device for traction tool actuation, which has a longitudinally movable piston loaded by a helical spring, in order to apply a linear force on the traction tool to be tensioned drive on. In the tensioning device disclosed here, only the intermediate forces acting on the bearings are active.

On the contrary, from DE 102 36 113 B3 known a kind of rotary support device with sliding bearing, this sliding bearing has a fixed ceramic body with bearing bearing surface. The ceramic material used has a high wear resistance and at the same time provides a reliable and long-lasting rotating bearing under large eccentric forces and a high temperature (for example, by friction).

The disadvantage here is that the ceramic body can only be inserted into a plain bearing bushing (sleeve) for accommodating the ceramic body with great effort, since this material is difficult due to its shape stability and is difficult to withstand at high Use under time consumption. Under increased pressure, the ceramic body can be destroyed due to its brittle material properties. The ceramic body can be inserted only by expensive and time-consuming heating of the slide bearing. Mounting of such swivel bearings has therefore proven to be complex and expensive.

This document therefore does not disclose any solution, how eg wear phenomena related to the pins (pins in the tensioner not made of ceramic but eg hardened steel) can be resolved. Overall, the plain bearings known here therefore also have a relatively short service life. Furthermore, calibration or limitation of tolerances has a negative impact on cost and service life.

Contents of the invention

The object of the present invention is how to achieve an increase in the service life of the slide bearing in a simple manner and with low structural outlay while maintaining the current installation procedures. A further object is to extend the limits of use of conventional plain bearings while at the same time maintaining the tolerances for pin diameter, housing diameter, and plain bearing wall thickness necessary for mass production.

This object is achieved by the features stated in the independent claims 1 and 4, while advantageous configurations and further developments of the invention are to be found in the dependent claims.

According to claim 1, the invention therefore relates to an end profile on a complementary slide bearing element, comprising a pin and at least one bearing bush for receiving the pin, which bears a bearing perpendicular to the pin-bearing bush The eccentric force acts on the unit, and the at least one bearing bush is designed to be cylindrical, and the pin is designed to gradually shrink toward the axial end direction from a predetermined position.

With this type of end profile configuration, the contact surface between pin and bearing bush is advantageously kept relatively large, especially under the action of an eccentric force, so that the pressure per unit area in the pin-bearing bush unit Significantly reduces and increases the service life of plain bearings.

The bearing structure of the tensioning unit constructed accordingly comprises a steel pin and a maintenance-free multi-component-slide bearing pair, which are pressed into the lever or base plate of the tensioning unit, for example in the receiving hole. According to a specific example, the concentricity error between the pair of slide bearings or their radial play should amount to a maximum of 20 μm. The calculation of the pressure per unit area in plain bearings results from the acting forces and the area of the force-loaded projection. Due to the significantly increased load area and consequently reduced pressure per unit area, wear phenomena are significantly reduced and the service life of the plain bearing is thus increased.

Furthermore, it is advantageous that inexpensive materials are available for the production of the pin and the bearing bush and that conventionally known production steps are available for the construction of the slide bearing. The service life of the plain bearing is thus increased while maintaining the same production costs. Furthermore, the current mounting regulations can be complied with and the service limits of the plain bearing can be extended while maintaining the tolerances of the components required for mass production.

Preferably, the tapering of the pin is designed radially. Due to the tapering "drum" shape of the pin, the pressure per unit area is reduced independently of the strength and direction of the eccentrically acting force. The radius of the drum shape can be selected individually according to different fields of application.

Preferably, the so-called predetermined position is arranged symmetrically about the axial midpoint of the pin. This type of pin construction enables a uniform reduced pressure per unit area on both sides, not only the left side of the plain bearing but also the right side of the plain bearing. In addition, it is advantageous to produce symmetrically designed pins.

In an embodiment instead of the features of claim 1 , the pin is designed cylindrically, while the inner wall of the at least one bearing bush is designed to taper starting from a predetermined position in the direction of the axial end. In this variant, which appears to be a "mirror image" of the first embodiment, the pressure per unit area is also significantly reduced. However, this solution proves to be disadvantageous in production compared to the first embodiment, since the machining of the conical bearing bush can be more expensive than the production of the conical pin.

Preferably, the tapering of the bearing bush is designed radially. It is also advantageous that the predetermined position is arranged symmetrically with respect to the axial midpoint of said at least one cylindrical bush.

In a more advantageous embodiment of both variants, the pin is supported in two bearing bushes. By means of this embodiment, support is achieved in the region of a sufficient bearing surface and a simultaneously long design of the bearing, whereby high torques exerted by eccentrically acting forces can be absorbed. In addition, axial frictional forces are reduced. Overall material and manufacturing costs will be reduced. In this tapered design of the bearing bushes, the two bearing bushes are each designed to taper outwards towards their ends.

Preferably, the at least one bearing bush contains a sliding coating of bronze-PTFE on the inner wall. Bronze-PTFE has good sliding and frictional properties under good thermal conductivity and weak low temperature fluidity. In mechanical engineering, bronze-polytetrafluoroethylene is preferably used for the sliding bearing of the carriage guide and, for example, also for the sliding bearing at the same time.

Description of drawings

The present invention will be described in more detail based on an embodiment. To this end the description is accompanied by the following drawings.

In the attached picture:

Fig. 1 according to the pin of the present invention - the end profile structure of the bearing bushing unit;

Fig. 2 according to the end profile structure of the pin-bearing bush unit in the prior art;

Figure 3 The pressure distribution per unit area on the paired sliding bearings;

Fig. 4 Cross-section with a tensioning system.

Detailed ways

FIG. 4 therefore shows a cross section through a belt tensioning system 1 with eccentrically arranged tensioning pulleys. The belt tensioning system 1 comprises a lower cylindrical housing 3 and an upper cylindrical housing 5 which have an outer diameter and an inner diameter which are as equal as possible. The cylindrical housings 3 and 5 interact axially in such a way that they can rotate relative to each other about a longitudinal axis 6 . The upper cylindrical housing 5 contains a side-mounted lever 8 , where the tensioning wheel is fastened by a screw 9 .

The radial inner surface of the upper cylindrical housing 5 is connected in a rotationally fixed manner to the axial end of a hollow pin 2 . The outer pin 2 has a rotationally fixed disk 4 on its other end, a friction plate 13 is arranged on its circular surface towards the lower cylindrical housing 3, and the friction plate 13 is mounted on the upper cylindrical housing 5, During the rotational movement of the pin 2 and the disk 4 relative to the lower cylindrical housing 3 , it absorbs, if necessary, coupled vibrations from the traction means. It is obvious that the pin 2 can also be designed without holes.

In order to deflect the upper cylindrical housing 5 relative to the lower cylindrical housing 3 and thus to press the tension pulley relative to the traction means of the traction means drive, a screw is arranged in the two cylindrical housings 3 and 5 The spring 7 exerts a force acting in the circumferential direction on the upper cylindrical housing 5 . An axial force is thus generated from the helical spring 7 and acts on the bottom area of the cylindrical housings 3 and 5 where the spring 7 is located, so that the lower cylindrical housing 3 is pressed against the friction disc 13 by a normal force. Tight on disc 4.

Furthermore, a two-part plain bearing bush 14 is pressed into the radially inner shell surface of the lower cylindrical housing 3 , the plain bearing bush 14 being made, for example, of steel with a bronze-polyester Sliding coating composed of a compound of vinyl fluoride. The hollow pin 2 is accommodated in the plain bearing bush 14 , the outer shell surface of which forms a friction pair with the bearing bush 14 .

As shown in Fig. 4, the forces acting on the tensioner pulley cause an eccentric load on the plain bearings (pin 2, bearing bush 14). Without the measures according to the invention, this would result in increased edge loading of the slide bearing element, which would lead to an increased pressure per unit area, with the result that the service life of the slide bearing would be reduced.

3 schematically shows the distribution of the pressure per unit area p on sliding bearings 14 constructed in pairs in a tensioning device according to the type, wherein a centrally acting force F (right illustration) and an eccentric, i.e. lateral Force F acting in the direction (left diagram). It can thus be seen that a centrally acting force results in a uniformly distributed load and pressure p between the bearing bush 14 and the pin 2 , which is schematically indicated by the hatched rectangular frame with ripples. This is very beneficial for achieving minimal bearing wear.

Correspondingly, without the constructive measures according to the invention, when a force F is introduced laterally into the plain bearing in the diagram on the left half of FIG. The triangular box with dimpled shading is shown diagrammatically.

As the force distribution curve shows, the load in the slide bearing is very inhomogeneous, and the opposing force peaks are formed intensified in the direction of the end of the slide bearing. In this case, therefore, very strong surface pressures act on the ends in each case, which lead to high wear in this area and thus reduce the service life.

FIG. 2 shows the configuration of the end profile on the pin bearing bushing unit 10 according to the background art together with the force F acting eccentrically on the cylindrical pin 12 . The pin 12 is supported here in two bearing bushes 14, 14' which are in turn pressed into the bushing 16. In this construction, the distribution of forces in the bushing-bearing bush unit 10 is very uneven, wherein there are strong force loads on each edge, which in turn leads to wear of the bushing-bearing bushing unit (cf. FIG. 3 , left half of the figure).

The descriptions listed in Fig. 2 concerning forces F, lengths L1, L2 and B, diameter BZ and materials refer to representative values in the field of application of belt tensioning systems and give exemplary explanations only .

FIG. 1 shows the configuration of the end profile of a pin-bearing bushing unit 20 according to the invention. Likewise a force F acts on the pin 22 eccentrically. Here too, the pin 22 is supported via two bearing bushes 24, 24' arranged axially one behind the other, which are pressed into bores in the housing 3. In the structural form of the present invention, the bearing bushes 24, 24' are designed to be cylindrical. On the contrary, when viewed from two positions separated by a distance Z, the pins 22 are designed to extend towards the axial end direction and gradually shrink. (drum-shaped). The tapering of the pin 22 is designed with a radius R in the radial direction. The center of the distance Z is at the same time the axial center of the pin 22 .

Due to the specific end profile configuration, the pressure per unit area is significantly reduced when the eccentric force F is applied, since the geometry of the shell surface of the pin 22 is already adapted to the so-called oblique pin load. The result is therefore that the load-bearing area between the pin 22 and the bearing bushing 24, 24' is significantly increased compared to known technical solutions, whereby the service life of the pin-bearing bushing unit 20 is maintained at the level of current installation regulations. will increase. At the same time, the limits of use of the pin-bearing bush unit 20 are widened while maintaining the tolerances necessary for mass production of the diameter of the pin 20 and the diameter of the bearing bushes 24, 24'.

The statements regarding forces F, dimensions and materials listed here in FIG. 1 also relate to typical values in the field of application of belt tensioning systems and are given as an example only.

It is therefore considered advantageous in the specific embodiment in FIG. 1 that when the force F acting together is 600 N, the distance L1 between the axial ends of the bearing bushes 24, 24' is 38.15 mm, each The axial length B of the bearing bush 24, 24' is 15mm, the length L2 in the pin 22 between the bearing bush 24 and the point of action of the force F is 20.85mm, the pin diameter BZΦ is 18mm, and the ends of the two pin surfaces The drum-shaped geometry of the zone has a radius R of 7350 mm, and the starting point (ie predetermined position) of the arc connected to this radius is separated by a distance Z of 10 mm. In the example described here, the starting point is also located 5 mm from the middle of the pin 22 .

The pin itself is made of material BZ=steel. The plain bearing comprises, in addition to the steel, a sliding coating consisting of a bronze-polytetrafluoroethylene compound.

list of reference signs

1 with tensioning system

2 pins

3 The lower cylindrical shell

4 discs

5 upper cylindrical shell

6 longitudinal axis

7 coil spring

8 leverage

9 bolts

10 Bushing-bearing bushing unit

12 pins

13 friction plate

14, 14' bearing bushing

20 Bushing-bearing bushing unit

22 pins

24, 24' bearing bushing

p pressure per unit area

F force

Claims (8)

1. end profile structure on the sliding bearing complementary elements, comprise that a pin (22) and at least one hold the bearing sleeve (24 of pin (22), 24 '), wherein this pin (22) bears one and holds the power (F) of the off-centre of lining unit (20) effect perpendicular to pin-shaft, it is characterized in that, described at least one bearing sleeve (24,24 ') is designed to cylindrical and pin (22) is designed to begin from preposition diminishing towards the axial end portion direction respectively.

2. by the described end profile structure on the sliding bearing complementary elements of claim 1, it is characterized in that dwindling gradually of (22) of pin is designed to radially.

3. by claim 1 or 2 described end profile structures on the sliding bearing complementary elements, it is characterized in that preposition is symmetrical in the axial midpoint setting of pin (22).

4. end profile structure, comprise that a pin (22) and at least one hold the bearing sleeve (24 of pin (22), 24 '), wherein this pin (22) bears one and holds the power (F) of the off-centre of lining unit (20) effect perpendicular to pin-shaft, it is characterized in that the inboard that described pin is designed to columniform and described at least one bearing sleeve is designed to begin from preposition diminishing towards the direction of axial end portion respectively.

5. by the described end profile structure of claim 4, it is characterized in that dwindling gradually of described at least one bearing sleeve (24,24 ') is designed to radially.

6. by claim 4 or 5 described end profile structures on the sliding bearing complementary elements, it is characterized in that preposition is symmetrical in the axial midpoint setting of described at least one bearing sleeve (24,24 ').

7. by the above-mentioned described end profile structure on the sliding bearing complementary elements of arbitrary claim, it is characterized in that pin (22) is bearing in two bearing sleeves (24,24 ').

8. by the above-mentioned described end profile structure on the sliding bearing complementary elements of arbitrary claim, it is characterized in that described at least one bearing sleeve (24,24 ') comprises the sliding coating that is made of bronze-teflon on inwall.

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